Turnbull heaped praise on China, Australia's largest trading partner, on Friday, saying Beijing's involvement in the latest set of UN Security Council sanctions was helping to "squeeze" North Korea into dropping its nuclear threats.

China, notwithstanding its "very close history with North Korea," had become part of global sanctions, especially by restricting oil exports into North Korea, Turnbull told Melbourne 3AW radio.

China, according to US estimates, controls 90 percent of North Korea's external trade. Russia also has considerable influence in Pyongyang. The latest sanctions particularly target the import of crude oil and natural gas products, and North Korea's textile exports.

Distributed via Jakarta

The letter entitled "Open Letter to Parliaments of Different Countries" was sent by North Korea from its embassy in Jakarta to the Australian embassy in Indonesia.

"It's basically a rant about how bad Donald Trump is," Turnbull said, referring to recent verbal exchanges between the US President and North Korean leader Kim Jong Un.

North Korea's Kim Jong Un celebrates September test

Australian Foreign Minister Julie Bishop said the letter was unusual because North Korea normally communicated with the outside world through its news agency KCNA.

"I think this shows they are feeling desperate, feeling isolated, trying to demonize the US, trying to divide the international community," Bishop told Australia's Fairfax Media.

Big miscalculation, says North

In a facsimile of the letter published by the Sydney Morning Herald, North Korea said "if Trump thinks that he would bring the DPRK, a nuclear power, to its knees through nuclear war threat, it will be a big miscalculation and an expression of ignorance."

The DPRK (the Democratic People's Republic of Korea) is North Korea's official name.

The council banned North Korea from importing natural gas liquids and condensates as well as crude oil imports and exports of North Korean textile products.

North Korean missile launches have caused alarm in South Korea. A television screen at a Seoul railway station in April

The sanctions also ban joint ventures and cooperative operations and bar any country from authorizing new work permits for North Korean workers — a major source of hard currency for the reclusive northeast Asian nation.

Uganda evicts military experts

In a further development reported Friday by Associated Press, Uganda said it had expelled North Korean military experts who for years have trained Ugandan security forces, including air force pilots.

Uganda's deputy minister of foreign affairs Okello Oryem said his nation was "in full compliance" with UN and US sanctions.

In 2014 while hosting a senior North Korean official, President Yoweri Museveni had described North Koreans as "friends who have helped Uganda for a long time."

Act as if 'on the cusp,' says CIA's Pompeo

Addressing a forum in Washington on Thursday, CIA Director Mike Pompeo said North Korea was still months away from perfecting its nuclear capabilities but urged Washington to behave "as if we are on the cusp" of Pyongyang achieving its objective.

Mike Pompeo, CIA Director

"We are at a time where the president has concluded that we need a global effort to ensure Kim Jong Un doesn't have that capacity," Pompeo said.

On Wednesday, Pompeo's predecessor John Brennan voiced concern about tweets broadcast by Trump and warned that prospects of nuclear conflict on the Korean Peninsula was "greater than they have been in several decades."

North Korea began its nuclear program decades ago and recently accelerated its weapons testing. Twice in July, it launched long-range missiles.